This project's goal is to develop a nonhuman primate model of learning and memory dysfunction in normal aging. Approximately 55 subjects 19 to 30+ years of age will be behaviorally tested over the course of the project. Younger subjects at 4-6 years of age serve as controls. A major aim of these investigations is to develop new learning and memory tasks for monkeys that are sensitive indicators of the relatively subtle neurobiological alterations associated with normal aging, particularly tasks exploring spatial learning and memory in freely moving subjects. Spatial information processing is significantly compromised during aging in rats and humans, and research focusing on this form of learning and memory has provided a valuable model system for studying the neural basis of age-related behavioral decline. Recent experiments have evaluated spatial working memory in young and aged monkeys using a large octagonal open field maze containing 8 reward locations distributed evenly around the perimeter of the apparatus, requiring subjects to learn to visit each location once per trial without returning to locations chosen earlier in the session. Similar to parallel studies in rats, a majority of young monkeys learn this procedure rapidly, requiring fewer than 20 trials to achieve a stringent performance criterion. Performance in aged monkeys, by contrast, is substantially more variable across individuals. Moreover, aged monkeys exhibit substantial deficits when the task requires retention of spatial information over delays ranging from 5 minutes to 4 hours. Additional task manipulations confirm that performance in young monkeys is guided by the distribution of spatial cues in the testing environment, and that aged monkeys perform nromally in a non-spatial version of the task. These findings parallel results from studies in rats, providing a valuable basis for establishing the generality of cognitive and neurobiological aging in rodent and primate models.